Glass-to-metal seal



Jn.. 4, 1944. PULFRlQH ETAL 2,338,538

GLAss-'ro-METAL SEALS Filed June 1, v1959 ng., l.

d Magn'er Y Inventors Hans PulFrich Ric ar Then Arizofney.v

Adifficulty is experienced surfaces.'

Um'rrzb STATES PATENT OFFICE f GLASS-To-METAL SEAL Hans Pulfrich, Berlin-Friedemann, and Richard Magnex', Berlin, Germany, assignors to General Electric Company, a corporation of New York Application June 1, 1939, Serial No. 276,928 A In Germany July 11, 1938 6 Claims.

The present invention relates to glass-tometal seals and more particularly to an improved method and means for sealing glass to iron. l

In joining iron to glass parts, considerable iny securing satisfactory adherence' of the iron and glass We lhave found that this difliculty may be substantially lessened by coating the iron with a layer of cobalt or molybdenum (preferably cobalt) and then annealing until an alloy is formed. Our invention in this connection may best be understood by reference to the following description and the accompanying drayving in which Figs. 1 andl 2 represent exemplary embodiments of the invention. u

In order to produce an adherence-improving coating of cobalt or molybdenum on an iron body it is convenient to apply the coating material by electrolytic deposition so as to form a plating. The coated iron part-is then annealed from one to five hours at 1000 to 1400 degrees- C. this beit especially advantageous to-use for the coning preferably done in a neutral gas such as hydrogen. The above specied heat treatment causes the cobalt (or molybdenum) to be diffused into the"l contains from 15 to 30% of cobalt at its outer Within this range the coefficient of expansion of the iron part is not seriously af- A fected by the addition'of the cobalt.

Surface For sealing with a metal part prepared in accordance with our invention, one may employ'a so-called soft glass, i, e., a glass with a coefcient of thermal expansion of from 80 10I to 100 l07' centimeters per centimeter per degree centigrade. One example of such a glass comprises the so-called Sendlinger glass which is free from lead and' which contains a substantial quantity of barium oxide. This glass has a coefficient of expansion of about 95 101. A

In Fig. l we have shown our invention as applied in connection with a'seal which comprises a metal sleeve l, a body of glass 2, and a, leadin wire 3 which passes through the body of glass. The sleeve is preferably 'constituted of iron having an alloyed surface prepared in accordance with the method described in the foregoing. The conductor 3 may be of similar composition if. desired.

We have found that superior results are obtained when the coefficient of expansion of the conductor 3 is from 1% to 10% above the. coefflcient of expansion of the glass. We consider ductor an alloy of from 40 to 50% iron with from Yto 50% nickel, such alloy being providedwithv a` superficial addition of cobalt or molybdenum (specifically, 1 to 5%) to improve adhesion.

Referring again to Fig. 1, the density of the stipping applied to the sleeve I is an indication of the varying concentration of the coating metal from pointto point in the iron. It will be noted that the sleeve is alloyed only on its innerA side, the outer side being preferably free from coating in order to facilitate Welding of the sleeve to other metal parts.

In Fig. 2 there is shown a sleeve provided with an annular flange 5. In this Acase the cobalt or molybdenum coating is preferably applied only to the cylindrical portion 6 of the sleeve, being excluded, for example, from the surface of the nange 5.

What we claim .as new and desire to secure by Letters Patent of the United States is:

1. A glass-to-metal seal including a body which consists mainly of iron, the outer layer of said body comprising an alloy of iron with a metal selected from the group consisting of cobalt and molybdenum, and a body of glass adhering to said alloy layer.

2. A glass-to-metal seal including a body which consists mainly of iron, the outer layer of said body comprising an alloy consisting substantially of iron and cobalt, and a body of glass fused to said layer, the content of cobalt in the alloy layer at the region of fusion with the glass being from about 15% to `about 30%.

I 3. A lead-in arrangement including a tubular iron sleeve having a layer of cobalt:iron alloy on the interiorl surface thereof; the cobalt content of said layer diminishing inwardly from the surface, a body of glass within the sleeve and sealed to the surface of said layer, and a conductor sealed through said glass and supported thereby in spaced relation to the sleeve, 'the content of cobalt in the said cobalt-iron layer at the region of fusion with the glass being from about 15% to about 30%.

said layer, a conductor sealed throughsaid glass and supported thereby in spaced relation to the sleeve, and a laterally extending ange at one end of the said sleeve, the surfaces of said flange being lfree of cobalt'to facilitate welding' of the flange to other metallic par-ts.

5. A glass-to-metal seal including a metal body, the outer layer of said body comprising an alloy of iron and cobalt and a body of glass fused to the surface of said alloy layer, the content of cobalt in the alloy at the glass Surface being about 15 to 30 per cent and the cobalt content diminishing from the surface toward the interior.

6. A body of glass having a coelcient of expension of about 80 to 100 107 cm. per cm. per degree centigrade, a. conductor sealed thereto which comprises an alloy of 40 to 50% iron and 60 to 50% nickel, and having the sealing surface thereof which is joined to said glass body alloyed with a metal chosen from the group comprising cobalt and molybdenum.

HANS PULFRICH. RICHARD MAGNER. 

